The present technology relates to a power receiving device and a power feeding system, and particularly to a power receiving device in a noncontact power feeding system for feeding power in an electrically noncontact manner, and the power feeding system.
In related art, a noncontact power feeding system for feeding power in an electrically noncontact manner may include a circuit for detecting, as foreign matter, an object got into a magnetic field between a power feeding device and a power receiving device. This is because when foreign matter as a conductor is present in the magnetic field, an eddy current occurs within the foreign matter, and the foreign matter may generate heat due to an effect of a Joule heat caused by the eddy current. A large amount of heat generated by the foreign matter may cause damage to a device or a casing in the noncontact power feeding system. In quick charging, in particular, the intensity of a magnetic field output by the power feeding device is increased, so that the amount of heat generated by the foreign matter is also increased. Thus, the presence of the foreign matter often becomes a problem.
A circuit that determines whether foreign matter is present or not on the basis of whether the amplitude of a voltage induced on a power receiving side is less than a reference value, for example, has been proposed as a circuit for detecting foreign matter (see Japanese Patent Laid-Open No. 2012-16125, for example). When foreign matter is present, the eddy current of the foreign matter causes a power loss, and decreases power transmission efficiency. It is thus determined that foreign matter is present when the amplitude of the voltage on the power receiving side is decreased to less than the reference value.